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Pojodojo asks: "I am doing an independent study next semester with my computer science professor which we decided to call Historic Microcomputer Repair and Restoration. I will be working with such classics as the Altair 8080 and the Apple II. After I have repaired and or restored these machines, I will put them in a display for others to see. I have the opportunity for a modest budget to get equipment to put in the display, and would like to know is, what sort of things would you as fellow comp sci geeks like to see in a Historic Computer exhibit?"

I'm not kidding. I remember having a disk of porn for the BBC Micro. That computer only had 32k of ram, and the porn I had was for a mode that used about 5k..perhaps 10, something like that. It was animated too - two frames of it. Amusing.

I had a lot of Beeb software but never stumbled across porn. It could have been mode 4 (2 colours, 320x256, 10k) or 5 (4 colours, 160x256, 10k). The only one using less ram was mode 7 (teletext, 1k) and somehow I don't think the pr0n would have looked too good in that, though I guess you'd have gotten plenty of frames.

.. I don't know the extent to which it fits your definition, but if I was to think of a bitchin' computer (insomuch as it could do some level of computing). It would be an Amiga 500, god I loved that... if you want something a little more in the line of "computer" I would say collosus, the original bletchly park beast... it could still out perform a P4....

You've got to love it that when a computer is so efficent that it's only limited by the speed at which data can be fed into it.

When testing to see how fast the Colossus could perform reliably, engineers found that it would perform flawlessly until it was running so fast that the paper tapes that fed the input data into Colossus caught fire, at which point they abandoned the experiment for fear that they'd burn the wood-framed building down. A true testament to Turing and the other fine scientists at Bletchly Park.

Pity Churchill ordered it destroyed after the war was over. It was decades ahead of its time.

No, the Colossi were not all destroyed, some continued into the late 50s where they were replaced by more modern equipment at GCHQ Cheltenham. The techniques used by Colossus remained applicable until well into the sixties are the Russians were using ciphers similar to the German Lorenz system.

The fact that Colossus existed was heavily guarded until Winterbotham's book (about 1974) so the remains were carefully destroyed as were most records of its construction. However Tony Sale managed to reconstruct it [codesandciphers.org.uk]

The claim probably comes from this incident [iankitching.me.uk]:(quote)A simulation of Colossus which Sale ran on a top-of-the-range Pentium PC took twice as long as the real thing.

or this [pgp.com]:If you wanted to program a modern computer to do what Colossus does, you'd need a 2GHz Pentium to match it.

Don't forget Colossus was massively parallel [codesandciphers.org.uk]:At 5,000 cps the interval between sprocket holes is 200 microsecs. In this time Colossus will do up to 100 Boolean calculations simultaneously on each of the five tape channels and across a

I'm not sure the Amiga 500 would be the most appropriate example; maybe either the 1000 (at one end of the scale) or the 4000 (at the other). I'd say the Amiga has a significant place in the history of home/personal microcomputers, as I regard it as the last in the line before x86 PCs took over.

The Amiga 1000 (the original Amiga) is the better historical computer, IMO. Hey - any movie used in The Price of Darkness has gotta have it goin' on!"I LIVE! I LIVE! I LIVE! I LIVE! I LIVE! I LIVE! I LIVE! I LIVE! I LIVE! "..."IN FACT...YOU WILL NOT BE SAVED!"

Classic.

Definitely the computer Matthew Broderick used in WarGames (IMSAI?) should be in there.

Scrounging up a working Apple Lisa and Apple/// would be good, same for a Kaypro and an Osborne. All the classic 8-bits: Atari 400 and 800, Commodore PET,

You know, I completely forgot the Radio Shack lines. The TRS-80 series were very popular, but let's not forget about the Color Computer series (CoCo) - which actually ran arguably the most sophisticated OS of the day - OS9. This system is still being developed for today (both new hardware and OS updates), amazingly enough. Very impressive.The Atari 800 design seems to be quite advanced in concept, but lackluster in execution. If you look at it, it's basically a badly-done Amiga. Custom chips, etc. The insis

The Apple II was arguably the micro with the greatest historical impact.

The first flight simulator was written for the Apple II, which triggered the imagination of a lot of people. But more importantly, the first electronic spreadsheet was written for the Apple II, and became an instant hit with accounting firms. Suddenly these micro computers were no longer just toys for guys who spent too much time with Popular Science; there might be money to be made with them, somehow...

I believe there was an external genlock for the Amiga 500. However, the Amiga 2000 was by far the more popular platform for business use, with or without the toaster. I used to have an A2000 with the internal genlock (used the video slot, same place the toaster taps into for video, while it also goes into a normal slot) and the only thing I ever used it for was to chat over television (output from my vcr, which has a tuner of course) but it was pretty spiffy and fairly decent-quality.

There was an amazing variety of 8-bit platforms manufactured between 1976-1985, the more you have the better. But take my advice, having refurbished a number of these machines: Plan on buying 3 for every one you get working, Ebay is your friend, no single machine is worth more than $5. You should be able to pick up core cpu/keyboards for $15 following these rules. Use a modern audio cable switch box and a single composite monitor to switch between them- Composite monitors are hard to find and expensive, but many modern cheap 15" TV sets have the correct RCA inputs.

Depends on how you look at it- 1976-1979 certainly had the big names come in (Commodore Pet, Vic 20 & 64; TI-99/4 and/4a, Apple I, II, II+, IIe, Altair, the Tandy Radio Shack series, and of course, who can forget the precursor to the BBC micro, the Timex Sinclair Z80?), all of which were TECHNICAL leaps forward. But the real explosion came in with the merging of the Home Video Game Industry with the Home Computer industry: Coleco Adam; Atari 400, 800, 1600. And of course the business machines from I

The x86 won the desktop war, but what about embedded systems? In this arena, there are more choices. Sure there are three major architectures: MIPS, ARM, PowerPC, but there are some lesser used systems, such as the Z80 and Motorola {6,8}800 (some), SPARC (a few). Most of these systems are nanos, and the moniker 'personal computer' may not apply to them, but computer geeks can still tinker with them. The lament, 'x86 is the only processor line left', is SO 1990's. Also, I think that most of the 'micro' comp

Quite a few other, lesser known, computers were made during that time as well. Finding techinal information and replacement parts (unique ones, like keys) on those machines is a real challenegeI've got about 3 Exidy Sorcerers (2 working), a couple APF imagination Machines (working), and a non-working Compucolor II (circa 1979).

Supposedly, only 4,000 Compucolor IIs were made, and I have to find any technical info on them. If any/. reader knows anything about them, drop me a line!

Which is why I suggested buying them in threes- most of the computers of this time period had three basic circuit boards in them: Keyboard, Power, Motherboard. IF you're lucky and don't have any hand-patched RevB boards, these three boards are usually interchangeable with a little work even without a tech manual of any sort; and by buying three units, you can usually cobble together one working machine between the three.

But I agree- some of these are INCREDIBLY hard to find even one of- your Compucolor i

People have a tendency to look at history of technoloy in a teleological sense: let's portray technology as an inexorable march towards the modern machines: for airplanes, you start with the Wright Flyer and you end with the A380. For Micros, you'd start with the Altair/Sol sort of stuff, and end with a dual-core dual-LCD screen workstation, some glowing riced-out gaming rig, a laptop, PDA and tablet PC.

who can forget the precursor to the BBC micro, the Timex Sinclair Z80?

No, the Sinclair ZX80 [old-computers.com] was the precursor to the ZX81 [old-computers.com] and ultimately the Sinclair Spectrum. [old-computers.com] The BBC Microcomputer [old-computers.com] was built by Acorn Computer, [wikipedia.org] who were rivals of Sinclair Research [wikipedia.org] in the competition for the BBC contract, and won because of clearly superior engineering. This rivalry became something of a personality clash between the founders of the two Cambridge-based companies: I remember reading reports of an altercation in a Camb

I realize that you're doing this as an independent study project for which the repair aspect is certainly a valuable learning tool. However, is repairing these machines particularly necessary? Will you power them up and leave them running in the display? I mean, unless you've got some decent demos running (and maybe I'm missing the point and that's exactly what you're asking for here), the machines will be sitting idle behind some plexi. In which case all you really need to do is clean them up to be present

Back around '93 me and a group of friends embarked on a project like this. Half the fun was actually getting the computers up and running. We were able to scrounge all manner of old computers and videogame consoles.Among our finds was a Commodore 64 with a blown VIC graphic chip. When turned on this computer just displayed a constantly changing flow of colors similar to those "plasma" color demos that were popular at the time.We had computers from houses near the ocean with corroded motherboards from the sa

is to stick with well documented hardware. The two you've picked so far ought to more than fit the bill, but considering you've added "repair" to the title of the class, I assume you'll be doing pcb level hardware repair. This is a LOT of fun and frustration at the same time, but if you start digging into machines that nobody's thought of, cared about, or kept track of over the past 30+ years you probably will start getting into headaches of trying to diagnose some seriously weird bugs. Not to discourage you from this course of action, in fact far from it, it sounds like something I would have enjoyed in my public schooling days (or at least getting credit for it). Find clubs that support the machines and can give you advice, don't try to go it alone, after all, the machines were built by teams, teams should help you rebuild them. Most of all remember to have fun!

Their collection of hardware is pretty much unmatched, and is open to the public. What's on display is the tip of their collection's iceberg. Who knows what might be kicking around in the background, just waiting for a small team of geeks to restore? [computerhistory.org]

And conversely, who knows what might be kicking around in your classmates' basements that's on CHM's wish list [computerhistory.org]?

Seconded and bumped +5. I was down there 3 weeks ago and have a CD full of pictures and videosfrom the tour.

Run, don't walk, to this museum. And if you really feel the need, Google is a few blocks away, Apple is a 10 minute drive, and a bunch of other fine folks. There's even the local Sports Bar, right across the street.

You might want to contact MARCH [midatlanticretro.org], The Mid-Atlantic Retro Computer Hobbyist group. They've only been around for a very short time, but they're gathering a lot of informative members. They are running an exhibit this weekend (May 13) in Wall, NJ. Their website is still just basic info, but they have a discussion forum on Yahoo as linked on their main page.

While most people don't think of them as "historic", displaying a 5 to 10 year-old computer and comparing it with a modern computer highlights the rapid pace of change in the industry and is interesting to see.

Here's some computers I'd recommend you try to get. Each represents one or more milestones to what we now consider commonplace. (I've left out some of the more obvious ones; please forgive me if I've named some you consider obvious.)

Atari 400/800/XL series. One of the first computers to feature separate programmable chips for CPU, I/O, sound and graphics, and much more sophisticated multi-mode interrupt-driven video than either of its 6502 peers, the Apple ][ and the C64. The first digitized video I was on was connected to an 800 and the first computer playback of music I ever heard came from it (10 scratchy seconds of "You Really Got Me" by Van Halen).Remarkably hackable OS for ROM firmware. Arguably the truest random number generator

One of them. The TI-99/4A did as well- and then they gunked it up by abstracting BASIC behind two levels of interpreters. If you were lucky enough to have the Editor/Assembler Cartridge and learn 16-bit Assembly, you quickly found out that the darned thing actually had 4 sub processors (Graphics/Video, Mathematical, Sound, Memory/Peripherial) with their own memory spaces, and that almost every peripherial you added to it added a small amount of memory + another processor. If you were intelligent about it

Actually, the video/graphics processor was the main CPU in the heart of that beast, right? In addition, it used video memory for main ram, rather than having dedicated memory for each.I only had the "mini memory" cartridge, and no good documentation, so I never learned a whole lot about the different things I could do with the TI. I really wanted the Editor/Assembler... later, I graduated to a CoCo3 with it's Assembler - that 6809 was a dream to program on.... (and since the Basic wasn't interpreted 6 wa

An interesting and somewhat rare one in the portable's category is the Commodore SX-64

Yes it is. I keep one on a table in my office for others to take notice of. I don't get as many questions about it as I first thought I would. I need to interface it with my office computer to give people something to "fiddle" with.

Probably the easiest computer to rebuild from the classic era as there is only one bus (Unibus), and nothing but traces and some very simple electronics on the backplane. Well that and you could hit them with a hammer.

The PDP-11 series, along with the PDP-8's were some of the first nodes on the ARPANET and you can still get working Ethernet adapters for them.

I don't know if the PDP-8 and 11 qualify as microcomputers; I always thought they were minis, but they sure were great boxes.

I have a Heathkit badged PDP-11/03 sitting at my parents house. It's no bigger than the original IBM PC, though I admit, I don't have a 8-inch dual disk unit that is supposed to be paired with it. The bigger Unibus machines were mini's. I'd consider the Q-Bus systems to be micros.

The Heathkit version is rather rare, I wonder if I need to find a collection to donate it to...

I too started out (at school) on a PDP-8/e with paper tape and teletypes and you are correct - it and the PDP-11 were minicomputers. Witness the fact that rather than containing a microprocessor they had multiple-board processors: "The first 6 cards is the CPU". [pdp8.net] (Don't blame me for the grammar, folks; I'm quoting.)

DEC did produce a PDP-11-on-a-chip called the T-11. [trailing-edge.com] For a while in the mid-80s I had a system based on it, which a friend who had a combination of too much scrap hardware and too much free tim

You can simulate it. There's a couple PDP-11 simulators that you can run on Linux that will actually boot V7 Unix images. I had it running back in 1996 or so... Always amusing to tie it to port 23 and leave it on the net for the script kiddies to play with....

i've actually been getting back into it, and i'm writing a BASIC interpreter in my new language of choice, and i've been picking up old applesoft BASIC manuals on ebay... really fun

what language? is it working?

I still have all my apple ][ disks with all my basic programs from those days, and my beagle bros peeks & pokes chart. it was good, indeed. but those days are long gone, and all that work is hidden away on disk, on fading cheap fanfold paper, etc. I've been thinking over the years of ways to keep/

This isn't something one could easily acquire or build, but I recently saw a demo of an 8-bit relay computer [pdx.edu] built by one of the professors at my school. It is constructed from 415 relays (electrically actuated mechanical switches) wired together, and is capable of addition, and, or, xor, not, conditional jumps, shift left and a few other misclaneous instructions I can't recall.

Mr. Lee worked out the server methodology for serving up the web and it was the forerunner of the operating system and dev-tools of the current OSX environ. Plus you don't see many working cubes these days - at least with working Magneto-Optical drives. Another triva note - the engine for the first iteration of Doom was sussed out on NeXTstep. I have the binaries around somewhere...

All of those old machines had one flaw or another, something that came up even when brand new as a result of bad design -- having to lift and drop the LISA on occasion, for instance, or having to reseat the memory cards in Atari 800s every few days to keep 'em running.Given the premise of your work, I'd want to know what you fixed on each machine that was due to age and neglect, versus what you did (or didn't) fix because it was a side-effect of a known design flaw (such as impact damage to the bottom of th

I used a Texas Instruments PC (similar but
not compatible with IBM PC).
It had a disk controller board that had to go
to double character revision markings and *still*
had an unholy rat's nest of wires. The motherboard
was not much better.

RS 6000 desktop under a desk at my job at IBM. Don't know much more about it, but it was good for a "woa...um, I don't support those" comment.My old roommate used to cart around some huge spark box from apartment to apartment...had like 8 processor boards. He never got it running, but it would boot. We almost had a computer museum in our 3rd bedroom "NOC"...thank god for all-bills paid apartments with a good net connection. I think he had some Amiga box, maybe even a commodore 64. I remember him playin

True! A 300 baud acoustic modem is a must. In the late 70's and early 80's, these were just barely legal. You leased you phone from "ma bell", and were not supposed to attach unapproved devices to "their wiring". The acoustic coupler skirted these rules quite effectively.

It depends on the degree of anality the museum displays in the choice and care of their exhibits. This will severely restrict your options if you have to replace components to make the computers operable.

Over the last 28 years I've worked at several railroad museums (as a volunteer), and one was extremely anal about the "originality" of the rolling stock.

For example, about 40 years ago they were given a functionning 100 year old steam locomotive, but they totally neglected it because over it's century of

Dot matrix and daisywheel printers.Paddle wheels and joysticks (good lord they were so primitive!)Green phosphor and amber phosphor CRTsCassette tapeAcoustic coupler modemMockingboard sound cardExternal keyboard (with lowercase letters!) that attached via an umbilical.CP/M Card80-column cardOh, and a box of 5 1/4" floppy disks, and a flippy-notcher to use the back, and a Beagle Bros poster to complete the scene.

This make me nostalgic for the CP/M card and the Videx 80-column conversion that let me run WordS

I feel like the altair / apple / C= stuff has all been done over many times....Someone mentioned the sinclair, that might be interesting, especially if you could find one of the color ones. PDPs and the like fall in with one of my favorites, the Pr1me, as being mini-computers.How about an Alpha-Micro? It dates to about 1982, so while not _super_ old, it's no spring chicken. The company still exisits in some form, so you might be able to get docs, schematics, etc. And that whole 'write your backups to a VHS

I'm not sure whether this can be easily retrofitted into other computer designs, but one of the coolest things on the LINC [wikipedia.org]--sometimes billed as "the first personal computer"--was the adjustable speed.

The LINC had a pair of dials on it: one was a (continuous) potentiometer, like a volume control, the other was a four-position "decade" switch. The pair of dials joint produced a signal that could be used to make any of a number of front-panel functions auto-repeat at a variable rate. In particular, you could make the "single-step" function auto-repeat. The pot adjusted the repeat rate continously over about a ten-to-one range. Each switch position was a factor of ten faster than the last. The slowest speed was about two per second.

This means that you could make the LINC single-step through its programs at an rate from about 2 to 200,000 steps per second... the later being about half of its full speed.

So, you could take a program... run it at 2 steps per second and watch the lights flash... then gradually speed it up over a five decades to 200,000 steps per second. At 2 steps per second if you watched closely from time to time you'd see one dot on the screen flash momentarily. As you sped it up the, the flashes would occur more rapidly... then you could see it was forming characters... then lines of text appearing at about the speed of a dot matrix printer... then finally a whole screen of flicker-free text.

Meanwhile, the LINC's speaker, attached to bit 6 of the accumulator, would gradually change from ticks to a buzzes to beeps.

I never saw anything that gave you such a feeling for just how incredibly goddam fast a computer was. Even one running at about 0.5 megahertz clock rate.

You actually could build a LINC from scratch, I suppose, since it was discrete components and the design was public domain. But it would be equally interesting to take a "stock" computer of almost any vintage and give it a continuously variable clock, a la the LINC.

In Some respects, this may seem a little too new for what you're trying to do, but I'm going to throw it out anyway: A 286 with Wing Commander with an original Sound Blaster. I think a lot of people here would agree that WC was a major milestone in PC Gaming. For a while, Wing Commander was the game you built your machine around.

Erm, this would appeal to *ME*, but I don't know how well it'd work for you. The pre-Wolfenstein days are pretty interesting.

I've got many emails over the years on asking verious questions on repairing old PETs (I have a couple simple fixes like check the sockets, clean contacts etc. but I'm not a hardware guy). The popular classic computers like the Atari 800, Apple II, VIC, C64, etc. have some really nice troubleshooting cheatsheets and guides, usually with text like 'if this is the symptom, check and/or replace these items..' Unfortuantely for the less popular machines (PET, Coleco Adam, etc, etc) there are no or very few guides.

If you did your repairs and also worked up some rudimentary troubleshooting guide (or better set up a Wiki) for others I think you would be doing a bigger service to the classic computer communtity than just some me-too restorations.

If you want a challenge for a restoration I would go and get a classic system restored and running, then gather a bunch of choice apps for the system and code up some easy front end (on that system or use a virtual drive, something friendlier) to demonstrate the actual programs in an "exhibit environment" (easy reset/reload, nice menu, etc.), a computer that successfully lights READY. is one thing, but one that also presents a menu of some of the popular games or programs of the time to experience is something way better.

A chip puller (looked like an oversized tweezer with prongs bent inward)

A chip setter. Get the complete set that would handle small, medium and large chips (8, 16, and 32 leg chips)

The classic memory testing tools: a hair dryer with the nozzle stepped down with duct tape and cardboard so you could reliably heat just one chip at a time, and a can of freon spray with the long tube so you could cool the chip you just brought to failure temperature befo

Get everything you can find that remotely resembles a classic computer. You can sort it out later. If space is a problem, split the collection across the basements/closets of several people in your group. I got a lot of stuff (mostly broken) that is sitting in storage, waiting for my retirement so that I may fix them in about 25 years.Whatever you do, think about it as saving the stuff from going to a landfill overseas, which is where this stuff is heading. You'd be surprised as to who may want to buy some

If he were a really old geek he'd have mentioned that he and Ada Lovelace used to sip tea whilst bragging about staying awake until the sun came up weaving towels out of nothing but some thread and the quadratic formula.

Hah! I cut my teeth on a teletype hooked up to a university mainframe. I was six, my friend's dad was a comp-sci professor. He let me play lunar lander and hunt the wumpus on his uni account.After that, it was a TRS-80 model I my dad bought in'79 or '80. We had an account with CompuServ and Genie and a 300 baud modem. Later he got the expansion interface with floppy drives, woot!

My first computer was a TI99 4/A. After that I owned a Commodore 64, and that was when I really go into the BBS scene. My friends

"you could get a version of MS-DOS that would run on these beasts."No you couldn't.Not unless there was an 8088 or 8086 card you could put in them. I guess it is possible such a beast was sold but they would have been rare.You could get CP/M for them and maybe ZPCR. I also remember a OS called LDOS I think was available as well.Now the Model 16 could run Xenix which was very cool.The first computer that Tandy made that ran MS-DOS I think was the Model 2000. It was better than the IBM CP but it wasn't PC com

That required an MSX computer. The TRS-80 Model 3 and 4 where not MSX systems. http://en.wikipedia.org/wiki/MSX [wikipedia.org] As you can see the TRS-80s didn't meet the MSX specs and Radio Shack had no interest making it. For the home/game market they where betting on the CoCo.Not to mention that MSX-Dos isn't MS-DOS.So no it didn't.

Agreed. The C64 has played a major role in the evolution of home computers. It sold a lot, sure, but most importantly, it was fun to learn, program and play with.

Of course, I'm biased. I remember when we went to the store in 1985 my parents and I, to buy our C64. It was supposed to be a much better system than the old TI-99 I had learned to type my name on, before I could even write it with a pen. When we got home, with the precious box, after many hours late at night, my father had to give up because the d